The present invention relates to an automatic audio signal level adjustment circuit capable of automatically adjusting a level of an input audio signal within a specific range.
Patent Reference has disclosed a conventional automatic audio signal level adjustment circuit. According to Patent Reference, the conventional automatic audio signal level adjustment circuit is configured to automatically decrease a gain of a variable amplifier when a level of an input audio signal is below a specific reference level. Further, the conventional automatic audio signal level adjustment circuit is configured to automatically increase the gain of the variable amplifier when the level of an input audio signal is above the specific reference level (refer to Patent Reference).
Patent Reference: Japanese Patent Publication No. 2006-041734
However, in the conventional automatic audio signal level adjustment circuit disclosed in Patent Reference, when the level of the input audio signal tends to fluctuate near the specific reference level, it is necessary to frequently switch from increasing the gain to decreasing the gain, or from decreasing the gain to increasing the gain, thereby causing a noise.
In view of the problems described above, an object of the present invention is to provide an automatic audio signal level adjustment circuit capable of solving the problems of the conventional automatic audio signal level adjustment circuit. In the present invention, it is possible to automatically adjust a level of an audio signal within a specific range while being capable of minimizing a noise.
Further objects and advantages of the invention will be apparent from the following description of the invention.